JP4770137B2 - Fuel cell system and operation method thereof - Google Patents

Description

  The present invention relates to a fuel cell system and an operation method thereof.

  Conventionally, since fuel cells have high power generation efficiency and do not emit harmful substances, they have been put into practical use as power generators for industrial and household use, or as power sources for artificial satellites and spacecrafts. Development is progressing as a power source for vehicles such as buses and trucks. The fuel cell may be an alkaline aqueous solution type, a phosphoric acid type, a molten carbonate type, a solid oxide type, a direct type methanol or the like, but a solid polymer type fuel cell is generally used.

  In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and integrated to join. When one of the gas diffusion electrodes is used as a fuel electrode (anode electrode) and hydrogen gas as fuel is supplied to the surface thereof, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into a solid polymer electrolyte. Permeates the membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidant is supplied to the surface, oxygen in the air is combined with the hydrogen ions and electrons to generate water. The An electromotive force is generated by such an electrochemical reaction.

  In the polymer electrolyte fuel cell, since both sides of the polymer electrolyte membrane need to be kept wet, water is supplied to the fuel electrode side and the oxygen electrode side, respectively. In this case, moisture moves as proton-entrained water from the fuel electrode side toward the oxygen electrode side, and moves as back diffusion water from the oxygen electrode side toward the fuel electrode side.

  By the way, if excessive water is retained from the oxygen electrode side to the fuel electrode side, sufficient supply of hydrogen and oxygen is hindered, so it is necessary to discharge excess water. In this case, excess moisture on the oxygen electrode side can be released into the atmosphere together with air, but excess moisture on the fuel electrode side restricts the release of hydrogen into the atmosphere from the viewpoint of safety. For example, when a vehicle equipped with a fuel cell is in an environment where hydrogen is difficult to diffuse, such as in tunnels and indoor parking lots, when hydrogen is released to discharge excess water, the hydrogen concentration around the vehicle increases, The possibility of explosion is increased.

Therefore, a technique has been proposed in which hydrogen discharged from the fuel electrode is recirculated to the hydrogen supply pipe and excess water contained in the hydrogen is recovered in a container such as a reserve tank (see, for example, Patent Document 1). .)
JP 2003-317753 A

  However, in the conventional fuel cell system, even if excess water is collected in the container, the amount of water collected and stored in the container increases with time. It is necessary to discharge hydrogen into the atmosphere every predetermined time. Therefore, when the vehicle equipped with a fuel cell is in an environment where hydrogen is difficult to diffuse, such as in tunnels and indoor parking lots, when the moisture is discharged, the hydrogen concentration around the vehicle increases, and an explosion can occur. It will be high.

  Of course, it is conceivable to attach a water level sensor to the container and discharge only the water without mixing hydrogen, but in this case, it is possible to cope with the load of the fuel cell that changes every moment, or to count the load. Therefore, the control becomes complicated and the apparatus configuration becomes complicated.

  The present invention solves the above-mentioned conventional problems, discharges excess reverse diffusion water together with the fuel gas to prevent clogging of the fuel gas flow path, and separates the reverse diffusion water from the discharged fuel gas. The fuel cell stack can be configured with a simple configuration by allowing the recovery container to accommodate the amount of reverse diffusion water estimated based on the amount of fuel gas supplied to the fuel cell stack. It is an object of the present invention to provide a fuel cell system that can collect and reuse dry fuel without increasing its size, and can eliminate the need for hydrogen discharge during normal operation of a vehicle, and an operation method thereof. To do.

Therefore, in the fuel cell system of the present invention, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is laminated with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell stack; a fuel supply line connected to the inlet of the fuel gas flow path; a fuel discharge pipe connected at one end to the outlet of the fuel gas flow path and connected at the other end to the fuel supply line And a pump that is provided in the fuel discharge pipe and discharges back diffusion water from the fuel electrode to the fuel discharge pipe and supplies the fuel gas discharged from the fuel gas flow path to the fuel supply pipe And a recovery container provided in the fuel discharge line and having a capacity larger than the amount of reverse diffusion water recovered when all the fuel gas stored in the fuel storage means connected to the fuel supply line is consumed. , The times containment Provided in the lower part, during operation of the fuel cell stack is blocked from the outside, having a water discharge conduit which is open to the outside when stopping the operation of the fuel cell stack.

  In another fuel cell system of the present invention, the fuel cell stack further includes an exhaust pipe having one end connected to the fuel discharge pipe and the other end opened to the atmosphere, and the exhaust pipe includes the fuel cell stack. And an exhaust on-off valve that is opened when the operation is stopped.

  In still another fuel cell system of the present invention, the exhaust pipe further includes a hydrogen combustor.

  In still another fuel cell system of the present invention, the fuel cell stack is a power source of a vehicle, and the amount of reverse diffusion water is estimated based on the amount of fuel gas mounted on the vehicle.

In the operation method of the fuel cell system of the present invention, the fuel gas is supplied from the fuel storage means to the fuel gas flow path of the fuel cell stack mounted on the vehicle, and the fuel gas discharged as an unreacted component is supplied to the fuel gas flow. A fuel cell system operating method for returning to a road, wherein one end of a fuel discharge line connected to the fuel supply line is connected to an outlet of the fuel gas path, connect the fuel supply line to the inlet, the fuel discharge line, the times container having a capacity greater than despreading water recovered when consumed all the fuel gas stored before Symbol fuel storage means provided, when stopping the operation of the fuel cell stack, by opening the lower portion of the collection container to the outside as well as blocking the conduction of the previous SL fuel discharge line and the fuel supply conduit, housed in the collection container Reversed The watering, to discharge into the atmosphere.

According to the present invention, in a fuel cell system, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is laminated with a separator having a fuel gas flow path formed along the fuel electrode. A fuel cell stack; a fuel supply line connected to the inlet of the fuel gas flow path; a fuel discharge pipe connected at one end to the outlet of the fuel gas flow path and connected at the other end to the fuel supply line A pump that is provided in the fuel discharge pipe and that supplies the fuel gas discharged from the fuel gas flow path to the fuel supply pipe; and is provided in the fuel discharge pipe and is connected to the fuel supply pipe. A recovery container having a capacity larger than the amount of back-diffusion water recovered when all of the fuel gas stored in the connected fuel storage means is consumed, and a lower part of the recovery container, and during operation of the fuel cell stack Shut off from the outside, Having a water discharge conduit which is open to the outside when stopping the operation of the charge cell stack.

  In this case, when the fuel gas mixed with the back diffusion water surplus in the fuel gas passage is discharged to the outside of the fuel cell stack, the recovery water separates the diffusion water and the fuel gas. The recovered fuel gas can be recovered and reused, and only the diffusion water can be selectively discharged. Thereby, the fuel consumption of a fuel cell stack can be suppressed.

  Further, since the fuel electrode is humidified by the reverse diffusion water and the mechanism for supplying water to the fuel gas flow path is not provided, the configuration of the fuel cell stack can be simplified and the size can be reduced. Furthermore, since it is not necessary to add moisture to the fuel gas and humidify it, there is no need to provide piping or control valves for introducing water into the fuel supply line, simplifying the configuration of the fuel cell system and reducing costs. Can be suppressed.

  Furthermore, since the recovery container can accommodate the amount of reverse diffusion water estimated based on the amount of fuel gas supplied to the fuel cell stack, the configuration of the recovery container can be simplified and the cost can be reduced. Moreover, it is not necessary to discharge hydrogen from the collection container to the atmosphere during normal operation of the vehicle.

  In another fuel cell system, the fuel cell stack further includes an exhaust pipe having one end connected to the fuel discharge pipe and the other end opened to the atmosphere, and the exhaust pipe operates the fuel cell stack. An exhaust on-off valve that is opened when stopped is provided.

  In this case, when the fuel cell stack is stopped, the fuel gas remaining in the fuel gas passage can be quickly discharged.

  In still another fuel cell system, the fuel cell stack is a power source of a vehicle, and the amount of reverse diffusion water is estimated based on the amount of fuel gas mounted on the vehicle.

  In this case, it is not necessary to discharge the fuel gas from the collection container to the atmosphere during operation of the vehicle.

According to the present invention, in the operation method of the fuel cell system, the fuel gas is supplied from the fuel storage means to the fuel gas flow path of the fuel cell stack mounted on the vehicle, and the fuel gas discharged as an unreacted component is An operation method of a fuel cell system for returning to a fuel gas flow path, wherein the other end of a fuel discharge pipe having one end connected to the fuel supply pipe is connected to an outlet of the fuel gas flow path, connect the fuel supply line to the inlet of the flow channel, the fuel discharge line, times having a larger capacity than the despreading water recovered when consumed all the fuel gas stored before Symbol fuel storage means the container is provided, when the user stops the operation of the fuel cell stack, by opening the lower portion of the collection container to the outside as well as blocking the conduction of the previous SL fuel discharge line and the fuel supply conduit, said collection container Housed in The inverse diffusion water is discharged into the atmosphere.

  In this case, since the recovery container can accommodate the amount of reverse diffusion water estimated based on the amount of fuel gas supplied to the fuel cell stack, the configuration of the recovery container can be simplified and the cost can be reduced. Moreover, it is not necessary to discharge hydrogen from the collection container to the atmosphere during normal operation of the vehicle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a diagram showing the configuration of the fuel cell stack in the embodiment of the present invention, FIG. 3 is a diagram showing the configuration of the cell module of the fuel cell in the embodiment of the present invention, and FIG. 4 is in the embodiment of the present invention. FIG. 5 is a second diagram showing the configuration of the separator of the fuel cell according to the embodiment of the present invention, and FIG. 6 is a cell of the fuel cell according to the embodiment of the present invention. FIG. 7 is a second enlarged sectional view showing the configuration of the cell module of the fuel cell according to the embodiment of the present invention, and FIG. 8 is a fuel cell according to the embodiment of the present invention. FIG. 9 is a schematic cross-sectional view showing the configuration of the unit cell of the fuel cell according to the embodiment of the present invention.

  In FIG. 2, a fuel cell stack 20 as a fuel cell (FC) is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts, and luggage carts. Here, the vehicle is equipped with a large number of auxiliary devices that consume electricity, such as lighting devices, radios, and power windows, and also has various driving patterns and requires a power source. Since the output range is extremely wide, it is desirable to use the fuel cell stack 20 as a power source and a secondary battery as a power storage means (not shown) in combination.

  The fuel cell stack 20 is of an alkaline aqueous solution type (AFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), direct methanol (DMFC), or the like. However, a polymer electrolyte fuel cell (PEMFC) is desirable.

  More preferably, it is called a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell or PEM (Proton Exchange Membrane) type fuel cell using hydrogen gas as fuel and oxygen or air as oxidant. Here, the PEM fuel cell is generally a fuel cell in which a catalyst, an electrode, and a separator are combined on both sides of a solid polymer electrolyte membrane as an electrolyte layer that transmits ions such as protons. Are composed of a plurality of stacks connected in series.

  In the present embodiment, the fuel cell stack 20 includes a plurality of cell modules 10 as shown in FIG. In addition, the arrow in FIG. 2 has shown the flow of the hydrogen gas as fuel gas. As shown in FIG. 3, the cell module 10 is introduced into the unit cell 10A while electrically connecting the unit cell (MEA) 10A as a fuel cell with the unit cell 10A. The separator 10B that separates the hydrogen gas flow path and the air flow path, and the two types of frames 17 and 18 that support the unit cell 10A and the separator 10B as one set, and multiple sets in the plate thickness direction (see FIG. 10 sets in the example shown in FIG. 3). Since the unit cell 10A is located inside the frame 18, it is not clearly shown in FIG. In the cell module 10, the unit cells 10A and the separator 10B are stacked in multiple stages using two types of frames 17 and 18 alternately as spacers so that the unit cells 10A are arranged with a predetermined gap (gap) therebetween. Are stacked. As shown in FIG. 4, one end of the cell module 10 in the stacking direction (upper end in FIG. 3) terminates at the vertical protrusion forming surface of the separator 10B and the end surface of one frame 17, and the cell module As shown in FIG. 5, the other end of 10 (the lower end in FIG. 3) terminates at the lateral ridge forming surface of the separator 10 </ b> B and the end surface of the other frame 18.

  6 and 7, the unit cell 10A includes a solid polymer electrolyte membrane 11 as an electrolyte layer and an oxygen electrode provided on one side of the solid polymer electrolyte membrane 11. As shown in FIG. It is comprised with the fuel electrode 13 provided in the air electrode 12 and the other side. 6 is an enlarged view of a part of the BB cross section in FIG. 4, and FIG. 7 is an enlarged view of a part of the AA cross section in FIG. The air electrode 12 and the fuel electrode 13 include a diffusion layer made of a conductive material that permeates while diffusing the reaction gas, and a catalyst material that is formed on the diffusion layer and is in contact with the solid polymer electrolyte membrane 11 to be supported. And a catalyst layer containing. Among these members, the air electrode 12 and the fuel electrode 13 have a lateral dimension slightly longer than the width of the opening of the frame 18 as a support member thereof and a vertical dimension slightly shorter than the height of the opening. It is said that. The solid polymer electrolyte membrane 11 has a vertical and horizontal dimension that is slightly larger than the vertical and horizontal dimensions of the opening.

  The separator 10B is provided on one side of the separator substrate 16 as a gas blocking member between the unit cells 10A and the separator substrate 16, and is in contact with the electrode diffusion layer on the air electrode 12 side of the unit cell 10A. In addition, an air electrode side collector 14 as a net-like current collector formed with a large number of openings through which a mixed flow of air and water is formed, and a fuel electrode 13 of the unit cell 10A provided on the other side of the separator substrate 16 are provided. And a fuel electrode side collector 15 as a net-like conductor for contacting the electrode diffusion layer on the side and leading out current to the outside. Then, in order to maintain these in a predetermined positional relationship including the unit cell 10A, the frames 17 (only the outermost ones have the upper and lower ends mutually connected to the backup plate 17a and the backup plate). And a frame 18 (see FIG. 4) connected to the plate 17b) and a frame 18 disposed on the peripheral edge of the fuel electrode side collector 15 and the unit cell 10A. In the present embodiment, the air electrode side collector 14 and the fuel electrode side collector 15 are formed of a thin metal plate, for example, one having a plate thickness of about 0.2 [mm]. The separator substrate 16 is formed of a thin metal plate having a thinner plate thickness. Examples of the constituent metal include metals having conductivity and corrosion resistance, for example, stainless steel, nickel alloy, titanium alloy and the like subjected to corrosion resistance conductive treatment such as gold plating. The frame 17 and the frame 18 are made of an appropriate insulating material.

  As shown in FIG. 4, the air electrode side collector 14 has a horizontally long rectangular shape (however, only the bottom is inclined to improve the draining effect). 8 has a mesh-like opening 143 having an opening ratio of 25% or more, as shown in detail on a larger scale (in order to make it easy to refer to the plate surface shape, only a part of the mesh shape is provided). Notation) It is made of a metal plate material and is a corrugated plate having fine ridges 141 formed by pressing. The ridges 141 are arranged so as to completely cut the plate surface at equal intervals parallel to the vertical side of the plate material (short side in the example shown in FIG. 8). The cross-sectional shape of the ridge 141 is roughly a rectangular wave-shaped cross-section, and the base side has a slightly flared shape due to the punching of the press work. The height of the ridge 141 is substantially the same as the thickness of the frame 17, thereby ensuring an air flow path having a predetermined opening area that vertically penetrates between the frames 17 on both sides in the laminated state. ing. The flat surface of the top 142 of each ridge 141 serves as a contact portion with which the air electrode 12 side diffusion layer comes into contact, and the valley portion 144 between the ridges 141 serves as a contact portion with the separator substrate 16. .

The air electrode side collector 14 is subjected to hydrophilic treatment. As a treatment method, a method of applying a hydrophilic treatment agent to the surface is employed. Examples of the treating agent to be applied include polyacrylamide, polyurethane resin, titanium oxide (TiO ₂ ), and the like. Examples of other hydrophilic treatment include treatment for roughening the roughness of the metal surface. For example, plasma processing is an example. The hydrophilic treatment is preferably performed on a portion where the temperature is highest, for example, on the top portion 142 of the convex portion 141 in contact with the unit cell 10A, particularly on the air flow path side. Thus, by performing the hydrophilic treatment, wetting (wetting) of the contact surface between the air electrode side collector 14 and the air electrode 12 side diffusion layer is promoted, and the effect of the latent heat cooling of water is improved. This also makes it difficult for water to clog the mesh openings, so that the possibility of water impeding the supply of air is further reduced.

  Further, the fuel electrode side collector 15 has a mesh-like opening 153 having the same dimensions as the air electrode side collector 14 (only a part of the mesh shape is shown for easy reference of the plate surface shape). A plurality of protrusions 151 are extruded and formed by pressing. The ridge 151 has a flat (simple) top portion 152 and a substantially rectangular wave shape as in the case of the ridge 141 described above, but the ridge in the case of the fuel electrode side collector 15. 151 are provided at a constant pitch in the vertical direction as extending in the horizontal direction completely across the plate surface. The planes of the top portions 152 of the ridges 151 serve as contact portions with which the fuel electrode 13 comes into contact, and the valley portions 154 between the ridges 151 serve as contact portions with the separator substrate 16. The cross-sectional shape of these ridges 151 is also roughly a rectangular wave-shaped cross-section, and the root side has a slightly flared shape due to die cutting in press working. The height of the ridges 151 is substantially the same as the thickness of the frame 18 together with the thickness of the unit cell 10A, and thereby a predetermined opening penetrating the inside of the frame 18 in the lateral direction in a stacked state. An area of fuel gas passage is secured.

  The air electrode side collector 14 and the fuel electrode side collector 15 are arranged with the separator substrate 16 interposed therebetween so that the protrusions 141 and the protrusions 151 are both outside. At this time, the trough portions 144 and trough portions 154 of the air electrode side collector 14 and the fuel electrode side collector 15 are in contact with the separator substrate 16 and are in a state where they can be energized with each other. Further, by superposing the air electrode side collector 14 and the fuel electrode side collector 15 on the separator substrate 16, an air flow path is formed on one side of the separator substrate 16 and a fuel gas flow path is formed on the other side. Become. Air and water are supplied from the vertical air flow path to the air electrode 12 of the unit cell 10A. Similarly, hydrogen is supplied from the horizontal fuel gas flow path to the fuel electrode 13 of the unit cell 10A. The

  In addition, a frame 17 and a frame 18 are disposed outside the separator 10B. As shown in FIGS. 6 and 7, the frame 17 surrounding the air electrode side collector 14 extends along the short side of the air electrode side collector 14 except for the outer end (the uppermost portion in FIG. 6 and the left end in FIG. 7). Only a vertical frame portion 171 that surrounds both sides is provided, and a long hole 172 that penetrates the vertical frame portion 171 in the thickness direction is provided for forming a fuel gas flow path. The thickness of the frame 17 is set to be comparable to the thickness of the corrugated air electrode side collector 14. Therefore, in a state where the frame 17 is combined with the air electrode side collector 14, the ridge 141 of the air electrode side collector 14 is in contact with the air electrode 12 of the unit cell 10 </ b> A, and the valley portion 144 is interposed via the separator substrate 16. The positional relationship comes into contact with the fuel electrode side collector 15. The separator substrate 16 has an outer dimension corresponding to the height and overall width of the frame 17, and is configured to include a similar long hole 162 at a position overlapping the long hole 172 of the frame 17. Thereby, between the vertical frame portions 171 of the frame 17, an air flow path that passes through in the vertical direction and is surrounded by the air electrode 12 surface of the unit cell 10 </ b> A and the separator substrate 16 is defined.

  The frame 18 that surrounds the fuel electrode side collector 15 and the unit cell 10A is configured to have the same size as the frame 17, but unlike the frame 17, the left and right vertical frame portions (in FIG. Although not shown in the figure, the horizontal width of the frame 17 having both ends at the same positions as the left and right ends of both vertical frame portions 171 of the frame 17 is substantially the same as the upper and lower horizontal frame portions) and the upper and lower horizontal bar portions 182. It is made into a complete rod shape with. The frame 18 extends in parallel with the left and right vertical bar portions except for the outer end (the bottom portion in FIG. 3, the surface shown in FIG. 5), and overlaps with the left and right ends of the fuel electrode side collector 15. 18a and a thick plate-like backup plate 18b, and a fuel gas flow path formation in which a space surrounded by the backup plate 18a and the vertical bar portion is aligned with a long hole 172 penetrating the frame 17 in the plate thickness direction. Make up space for. The thickness of the frame 18 is approximately equal to the thickness of the corrugated fuel electrode side collector 15 and the thickness of the unit cell 10A as described above. Therefore, in a state where the frame 18 is combined with the fuel electrode side collector 15, the protrusion 151 of the fuel electrode side collector 15 contacts the fuel electrode 13 of the unit cell 10 A, and the trough 154 passes through the separator substrate 16. The positional relationship comes into contact with the air electrode side collector 14. As a result, a fuel gas flow path in the frame stacking direction aligned with the long holes 172 of the vertical frame portion 171 of the frame 17 is formed between both vertical bar portions of the frame 18 and the backup plate 18a. Inside the frame 18, a fuel gas flow path as a lateral flow path sandwiched between the separator substrate 16 and the backup plate 18 a is defined by the waveform of the fuel electrode side collector 15.

  The frame 17 and the frame 18 thus configured hold the air electrode side collector 14, the fuel electrode side collector 15, and the separator substrate 16 to form the separator 10B. And the separator 10B and the unit cell 10A are laminated | stacked alternately, and the cell module 10 is comprised. As shown in FIG. 3, the cell modules 10 stacked in this way are entirely passed from the upper surface of the cell module 10 to the lower surface of the cell module 10 in a portion between the frames 18. A slit-like air flow path is formed.

  And in unit cell 10A, as FIG. 9 shows, water moves. In FIG. 9, 48 is a fuel chamber as a fuel gas flow path, and 49 is an oxygen chamber as an air flow path. In this case, when hydrogen gas is supplied as fuel gas into the fuel chamber 48 of the fuel electrode side collector 15, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are accompanied by proton-entrained water, resulting in a solid polymer. It passes through the electrolyte membrane 11. When the air electrode 12 is used as a cathode electrode and air as an oxidant is supplied into the oxygen chamber 49, oxygen in the air is combined with the hydrogen ions and electrons to generate water. Moisture permeates through the solid polymer electrolyte membrane 11 as reverse diffusion water and moves into the fuel chamber 48 of the fuel electrode side collector 15. Here, the reverse diffusion water means that the water generated in the oxygen chamber 49 diffuses into the solid polymer electrolyte membrane 11 and permeates through the solid polymer electrolyte membrane 11 in the direction opposite to the hydrogen ions. It penetrated up to 48.

  Next, the overall configuration of the fuel cell system will be described.

  FIG. 1 is a diagram showing a configuration of a fuel cell system according to an embodiment of the present invention.

  In FIG. 1, a device for supplying hydrogen gas as a fuel gas and air as an oxidant to a fuel cell stack 20 is shown. Although hydrogen gas, which is fuel taken out by reforming methanol, gasoline, or the like by a reformer (not shown), can be directly supplied to the fuel cell stack 20, it is stable and sufficient even during high-load operation of the vehicle. In order to be able to supply an amount of hydrogen gas, it is desirable to supply the hydrogen gas stored in the fuel storage means 73. Accordingly, hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell stack 20 can follow the fluctuation of the load on the vehicle and supply a necessary current. In this case, the output impedance of the fuel cell stack 20 is extremely low and can be approximated to zero.

  Hydrogen gas is stored in a container containing a hydrogen storage alloy, a container containing a hydrogen storage liquid such as decalin, a fuel storage means 73 such as a hydrogen gas cylinder, a first fuel supply line 21 as a fuel supply line, and The fuel is supplied to the inlet of the fuel gas flow path of the fuel cell stack 20 through a second fuel supply pipe 33 as a fuel supply pipe connected to the first fuel supply pipe 21. The first fuel supply pipe 21 is provided with a fuel storage means on-off valve 24, a pressure sensor 27, a first fuel pressure adjustment valve 25a, a second fuel pressure adjustment valve 25b, and a fuel supply electromagnetic valve 26. The The second fuel supply pipe 33 is provided with a safety valve 33a and a pressure sensor 78 for detecting the pressure in the fuel gas passage. The first fuel supply line 21 is connected to a start-up bypass line 22 for supplying hydrogen gas by bypassing the second fuel pressure regulating valve 25b when the fuel cell stack 20 is started. An activation fuel supply electromagnetic valve 23 is disposed in the activation bypass line 22. The fuel storage means 73 has a sufficiently large capacity and always has a capability of supplying hydrogen gas at a sufficiently high pressure. In the example shown in FIG. 1, a plurality of, for example, three fuel storage means 73 are provided, and the first fuel supply pipe 21 is connected to each fuel storage means 73 at a portion connected thereto. It is branched and is merged on the way to become one. However, the number of the fuel storage means 73 may be singular, plural, or any number in the case of plural.

  The hydrogen gas discharged as an unreacted component from the outlet of the fuel gas flow path of the fuel cell stack 20 is discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. A water recovery drain tank 60 as a recovery container is disposed in the fuel discharge line 31. The water recovery drain tank 60 is connected with a fuel discharge line 30 for discharging water and the separated hydrogen gas. The fuel discharge line 30 is provided with a suction circulation pump 36 as a pump. Yes. A hydrogen circulation electromagnetic valve 34 is disposed in the fuel discharge line 30. The end of the fuel discharge line 30 opposite to the water recovery drain tank 60 is connected to the second fuel supply line 33. Thereby, the hydrogen gas led out of the fuel cell stack 20 can be recovered and supplied to the fuel gas flow path of the fuel cell stack 20 for reuse.

  Further, a startup fuel discharge conduit 56 is connected to the water recovery drain tank 60, and a hydrogen startup exhaust solenoid valve 62 is disposed in the startup fuel discharge pipeline 56, so that the fuel cell stack 20 is started up. The hydrogen gas discharged from the fuel gas channel can be discharged into the atmosphere. Note that the outlet end of the starting fuel discharge pipe 56 is connected to an exhaust manifold 71 described later. Further, the starting fuel discharge pipe 56 branches from the middle, and the branch portion is connected to the fuel discharge pipe 30 between the suction circulation pump 36 and the hydrogen circulation electromagnetic valve 34. Further, a hydrogen start / stop electromagnetic valve 56a is disposed at the branch portion.

  Note that a hydrogen combustor may be provided in the startup fuel discharge line 56 as necessary. The hydrogen gas discharged by the hydrogen combustor can be combusted to form water, and then discharged into the atmosphere.

  Further, an outside air introduction line 28 is connected between the second fuel supply line 33 and the hydrogen circulation solenoid valve 34 in the fuel discharge line 30. The outside air introduction conduit 28 is provided with an outside air introduction electromagnetic valve 28a and an air filter 28b, and can introduce outside air into the fuel gas passage when the operation of the fuel cell stack 20 is completed. Yes.

  Here, the first fuel pressure regulating valve 25a and the second fuel pressure regulating valve 25b are those of a butterfly valve, a regulator valve, a diaphragm type valve, a mass flow controller, a sequence valve, etc., but the first fuel pressure regulating valve Any type of hydrogen gas may be used as long as the pressure of the hydrogen gas flowing out from the outlets of 25a and the second fuel pressure regulating valve 25b can be adjusted to a preset pressure. The pressure adjustment may be performed manually, but is preferably performed by an actuator including an electric motor, a pulse motor, an electromagnet, or the like.

  The start fuel supply solenoid valve 23, the fuel supply solenoid valve 26, the outside air introduction solenoid valve 28a, the hydrogen circulation solenoid valve 34, the hydrogen start / stop solenoid valve 56a, and the hydrogen start exhaust solenoid valve 62 are so-called on-off. It is of the type and is actuated by an actuator comprising an electric motor, a pulse motor, an electromagnet or the like. The fuel storage means original opening / closing valve 24 is operated manually or automatically using an electromagnetic valve. Further, the suction circulation pump 36 may be of any type as long as it can forcibly discharge the reverse diffusion water together with the hydrogen gas and can bring the inside of the fuel gas passage into a negative pressure state. Good. The air filter 28b removes dust, impurities, harmful gases and the like contained in the air.

  On the other hand, air as an oxidant is supplied from an oxidant supply source 75 such as an air supply fan, an air cylinder, or an air tank to an air flow path of the fuel cell stack 20 through an oxidant supply line 77 and an intake manifold 74. Supplied. Note that oxygen can be used as the oxidizing agent instead of air. The air discharged from the air flow path is discharged to the atmosphere through the exhaust manifold 71 and the condenser 72.

  The oxidant supply pipe 77 is provided with a water supply nozzle 76 for spraying water and maintaining the air electrode (cathode electrode) 12 of the fuel cell stack 20 in a wet state. Further, the air electrode 12 and the fuel electrode 13 can be cooled by the sprayed water. Further, the condenser 72 disposed at the end of the exhaust manifold 71 is for condensing and removing moisture contained in the air discharged from the fuel cell stack 20, and is condensed by the condenser 72. The water thus collected is collected in the water tank 52 through the condensed water discharge pipe 79. A drainage pump 51 is disposed in the condensed water discharge conduit 79, and a level gauge (water level gauge) 52a is disposed in the water tank 52.

  The water in the water tank 52 is supplied to the water supply nozzle 76 through the water supply pipe 53. A water supply pump 54 and a water filter 55 are disposed in the water supply line 53. Here, the drainage pump 51 and the water supply pump 54 may be of any kind as long as they can suck and discharge water. The water filter 55 may be of any type as long as it removes dust, impurities, etc. contained in the water.

  The secondary battery as the power storage means is a so-called battery (storage battery), and a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, a sodium sulfur battery, and the like are common. The power storage means does not necessarily have to be a battery, and electrically stores and discharges energy, such as a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil, and a pressure accumulator. Any form may be used as long as it has a function. Furthermore, any of these may be used alone, or a plurality of them may be used in combination.

  The fuel cell stack 20 is connected to a load (not shown) and supplies the generated current to the load. Here, the load is generally an inverter device that is a drive control device, and converts a direct current from the fuel cell stack 20 or the power storage means into an alternating current to rotate a vehicle wheel. To supply. Here, the drive motor also functions as a generator, and generates a so-called regenerative current when the vehicle is decelerated. In this case, since the drive motor is rotated by the wheel to generate electric power, the wheel is braked, that is, functions as a vehicle braking device (brake). Then, the regenerative current is supplied to the power storage means, and the power storage means is charged.

  In the present embodiment, the fuel cell system has control means (not shown). The control means includes arithmetic means such as a CPU and MPU, storage means such as a magnetic disk and a semiconductor memory, an input / output interface and the like, and is supplied from various sensors to the fuel gas flow path and the air flow path of the fuel cell stack 20. The flow rate of hydrogen, oxygen, air, etc., temperature, output voltage, etc. are detected, and the oxidant supply source 75, the first fuel pressure adjustment valve 25a, the second fuel pressure adjustment valve 25b, and the starting fuel supply electromagnetic valve 23 are detected. The operation of the fuel supply solenoid valve 26, the outside air introduction solenoid valve 28a, the hydrogen circulation solenoid valve 34, the suction circulation pump 36, the drain pump 51, the feed water pump 54, the hydrogen start / stop solenoid valve 56a, the hydrogen start exhaust solenoid valve 62, etc. Control. Furthermore, the control means controls the operation of all devices that supply fuel and oxidant to the fuel cell stack 20 in cooperation with other sensors and other control devices.

  Next, the configuration of the water recovery drain tank 60 will be described in detail.

  FIG. 10 is a diagram showing the configuration of the water recovery drain tank in the embodiment of the present invention.

  In the present embodiment, the water recovery drain tank 60 has a configuration as shown in FIG. The drain tank container 64 has a bottomed cylindrical shape, and an open upper part is hermetically closed (closed) by a container cover 66. The container cover 66 is fixed to the drain tank container 64 by fixing members 66a such as bolts, and an O-ring or the like is provided between the lower surface of the container cover 66 and the upper end surface of the drain tank container 64. A seal member is provided to maintain airtightness. The fuel discharge pipe 31 and the fuel discharge pipe 30 are connected to the side wall above the drain tank container 64 at positions separated from each other.

  Further, the capacity of the drain tank container 64 is set to be sufficiently larger than the amount of moisture recovered from the hydrogen gas discharged from the fuel gas flow path of the fuel cell stack 20. That is, the vehicle on which the fuel cell stack 20 is mounted once travels after filling the fuel storage means 73 with hydrogen gas as fuel, and then fills the fuel storage means 73 with hydrogen gas next time. During this period, the capacity of the drain tank container 64 is set to be larger than the amount of reverse diffusion water recovered from the hydrogen gas discharged from the fuel gas flow path.

  By the way, in the fuel cell system according to the present embodiment, water is not supplied to the anode electrode side as in the conventional fuel cell as disclosed in Patent Document 1. That is, the fuel cell stack 20 does not include a mechanism for supplying water to the fuel gas passage, and hydrogen gas supplied as fuel in the fuel gas passage is not humidified. In the fuel cell system in the present embodiment, the fuel electrode 13 is humidified by the reverse diffusion water. Thus, since the mechanism for supplying water to the fuel gas flow path is not provided, the configuration of the fuel cell stack 20 is simple and small. In addition, since it is not necessary to add moisture to the hydrogen gas and humidify it, there is no need to provide piping and control valves for introducing water into the first fuel supply line 21 and the second fuel supply line 33. The configuration is simple and the cost of the fuel cell system can be suppressed.

  And in the fuel gas flow path of the fuel cell stack 20, the surplus reverse diffusion water is mixed with surplus hydrogen gas to form a gas-liquid mixture. The gas-liquid mixture is sucked by the suction circulation pump 36 and led out to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. The gas-liquid mixture is introduced into the drain tank container 64 from the upper part of the water recovery drain tank 60. The gas-liquid mixture is separated into hydrogen gas and reverse diffusion water as moisture in the drain tank container 64, that is, the gas-liquid separated hydrogen gas is discharged out of the drain tank container 64 from the fuel discharge line 30. Is done. The separated reverse diffusion water is stored as stored water 65 in the lower part of the drain tank container 64. An activation fuel discharge line 56 is connected to the lower portion of the drain tank container 64 as a water discharge line in which a hydrogen activation exhaust electromagnetic valve 62 is disposed. In the present embodiment, the fuel electrode 13 is humidified by the reverse diffusion water and no mechanism for supplying water to the fuel gas flow path is provided. The amount of moisture contained is reduced. Therefore, the amount of water recovered from the hydrogen gas is reduced, and the capacity of the drain tank container 64 can be reduced.

  Next, a method for determining the capacity of the drain tank container 64 will be described.

  FIG. 11 is a diagram showing a change in the amount of water recovered in the water recovery drain tank in the embodiment of the present invention, and FIG. 12 is a diagram showing the water in the water recovery drain tank when the solid polymer electrolyte membrane is wet in the embodiment of the present invention. FIG. 13 is a diagram showing a change in the amount of reverse diffusion water with respect to the amount of hydrogen consumed in the embodiment of the present invention.

  First, when the temporal change in the amount of reverse diffusion water recovered from the fuel cell stack 20 was measured by an experiment, the result shown in FIG. 11 could be obtained. In FIG. 11, the vertical axis represents the amount of recovered reverse diffusion water [ml], and the horizontal axis represents time [minutes]. Here, the horizontal axis indicates the time from the start of the operation of the fuel cell system, and time 0 minutes is the time when the operation of the fuel cell system is started.

Here, the amount of reverse diffusion water collected is the total electrode area of the fuel cell stack 20, the current density of the fuel cell stack 20, the thickness of the solid polymer electrolyte membrane 11, and the gas diffusion constituting the fuel electrode 13 and the air electrode 12. Moisture permeability of electrode, humidity in fuel gas flow path, humidity in air flow path, pressure in fuel gas flow path, pressure in air flow path, temperature in fuel gas flow path, air flow path It can be expressed as a function of the temperature inside. The total electrode area of the fuel cell stack 20 used in the experiment is 22500 [cm ² ].

Therefore, FIG. 11 shows the result of measuring the temporal change in the amount of back-diffusion water for each current density of the fuel cell stack 20. The current density is a value obtained by dividing the current value output from the fuel cell stack 20 by the total electrode area of the fuel cell stack 20, and is represented by [A / cm ² ]. In FIG. 11, a curve 81 indicates a temporal change in the amount of recovered reverse diffusion water when the current density is 0.1 [A / cm ² ], and a curve 82 indicates a case where the current density is 0.2 [A / cm ² ]. Change over time in the amount of recovered reverse diffusion water, curve 83 shows the time change in the amount of recovered reverse diffusion water when the current density is 0.3 [A / cm ² ], and curve 84 shows the current density of 0.4. Change in reverse diffusion water with time in the case of [A / cm ² ], curve 85 shows change in reverse diffusion water with time when the current density is 0.5 [A / cm ² ]. ing. From this, it can be seen that the amount of reverse diffusion water increases as the current density increases.

  It can also be seen that the amount of reverse diffusion water hardly increases in the time zone immediately after the operation of the fuel cell system is started. This is considered to be because the back diffusion water does not permeate into the fuel gas flow path because the solid polymer electrolyte membrane 11 is dry in the time zone immediately after the operation of the fuel cell system is started. it can. Then, after a while has elapsed since the start of the operation of the fuel cell system, the solid polymer electrolyte membrane 11 becomes wet with the reverse diffusion water. Then, the reverse diffusion water penetrates into the fuel gas flow path, and the surplus reverse diffusion water is supplied to the fuel gas flow path and mixed with the surplus hydrogen gas to form a gas-liquid mixture to form the fuel cell. It is led out of the stack 20 and is collected as stored water 65 in the drain tank container 64. Therefore, the recovery amount of the reverse diffusion water is measured by measuring the amount of the stored water 65 in the drain tank container 64.

And based on the result shown by FIG. 11, the relationship between the collection amount of reverse diffusion water after the solid polymer electrolyte membrane 11 gets wet and the current density can be obtained. Here, the result shown in FIG. 12 could be obtained. In FIG. 12, the vertical axis represents the amount of reverse diffusion water recovered [ml], and the horizontal axis represents the current density [A / cm ² ].

In FIG. 12, a broken line 88 is a line connecting points indicating the relationship between the amount of reverse diffusion water recovered after the solid polymer electrolyte membrane 11 is wet and the current density obtained based on the result shown in FIG. A straight line 89 is an approximate straight line of the broken line 88. The straight line 89 can be expressed by the following equation (1).
Q1 = aI Formula (1)
Here, Q1 is a recovery amount per unit time [ml] as a recovery amount of reverse diffusion water per unit time, and I is an average value of current density [A / cm ² ]. Further, a is a constant for drawing the straight line 89. For example, the straight line 89 can be drawn by setting a to a value of 0.197975. When the polygonal line 88 is approximated, a curve represented by a polynomial is obtained. However, since a higher-order term of the second or higher order is a negligible value, it is omitted, and a straight line 89 represented by the equation (1) did.

  FIG. 13 shows the result of measuring the relationship between the amount of consumed hydrogen and the amount of reverse diffusion water recovered, that is, the amount of generated reverse diffusion water. In FIG. 13, the amount [ml] of reverse diffusion water generated on the vertical axis is taken, and the amount of hydrogen [l] consumed on the horizontal axis.

  In FIG. 13, a broken line 86 indicates the relationship between the measured amount of consumed hydrogen and the amount of generated reverse diffusion water, and a straight line 87 is an approximate straight line of the broken line 86. A straight line 91 parallel to the vertical axis indicates the amount of hydrogen gas charged in the fuel storage means 73 mounted on the vehicle, that is, the amount of hydrogen consumed. FIG. 13 shows an example in which the on-board hydrogen consumption is 2000 [l]. A straight line 92 parallel to the horizontal axis passing through the intersection of the straight line 87 and the straight line 91 is generated when the fuel cell stack 20 consumes all the hydrogen gas filled in the fuel storage means 73 mounted on the vehicle. The amount of reverse diffusion water to be produced, that is, the expected amount of reverse diffusion water is shown.

  Here, the expected amount of reverse diffusion water is determined by the flow of the fuel gas between the time when the fuel storage means 73 is once filled with the hydrogen gas as the fuel and the vehicle travels until the next time hydrogen gas is filled into the fuel storage means 73. This is the maximum amount of water recovered from the hydrogen gas discharged from the passage. Therefore, if the capacity of the drain tank container 64 is set to be larger than the expected amount of reverse diffusion water, the vehicle on which the fuel cell stack 20 is mounted once travels after filling the fuel storage means 73 with hydrogen gas as fuel. It is not necessary to drain water from the water recovery drain tank 60 until the next time hydrogen gas is filled into the fuel storage means 73.

  Next, the operation of the fuel cell system having the above configuration will be described.

  FIG. 14 is a first diagram for explaining the operation of the fuel cell system according to the embodiment of the present invention, FIG. 15 is a second diagram for explaining the operation of the fuel cell system according to the embodiment of the present invention, and FIG. It is a 3rd figure explaining operation | movement of the fuel cell system in embodiment of invention. 14 to 16 schematically show only the configuration of the portion related to the description of the operation in the fuel cell system.

  First, the operation in steady operation will be described. During steady operation in the fuel cell system of the present embodiment, after adjusting the pressure of hydrogen gas flowing out from the outlets of the first fuel pressure adjustment valve 25a and the second fuel pressure adjustment valve 25b to a predetermined constant pressure, The first fuel pressure adjustment valve 25a and the second fuel pressure adjustment valve 25b are not adjusted during operation of the fuel cell system, and are maintained as they are. Further, the oxidant supply source 75 always operates so as to supply a constant amount of air to the air flow path of the fuel cell stack 20. In this case, the amount of air supplied is an amount sufficiently larger than the amount of air necessary for the output of the fuel cell stack 20 to be maximized.

  When the fuel cell stack 20 starts operation, reverse diffusion water is generated in each unit cell 10A constituting the fuel cell stack 20, and the reverse diffusion water permeates the solid polymer electrolyte membrane 11 to flow the fuel gas. It penetrates to the road and humidifies the fuel electrode 13 side of the solid polymer electrolyte membrane 11. Thereby, the fuel electrode 13 side of the solid polymer electrolyte membrane 11 is in a wet state, and hydrogen ions generated from hydrogen by an electrochemical reaction can move smoothly in the solid polymer electrolyte membrane 11.

  Further, the hydrogen gas as an unreacted component that is supplied to the fuel gas flow path and surplus is mixed with the back-diffused water that has permeated into the fuel gas flow path and becomes surplus, and a gas-liquid mixture Become. The hydrogen gas that has become the gas-liquid mixture is sucked by the suction circulation pump 36 and led out of the fuel cell stack 20 through the fuel discharge pipe 31 connected to the fuel cell stack 20. The gas-liquid mixture passes through the fuel discharge pipe 31 and is introduced into the water recovery drain tank 60. Then, by staying in the water recovery drain tank 60 having a relatively wide space, heavy moisture falls downward due to gravity, and the reverse diffusion water is separated from the hydrogen gas. The hydrogen gas in a state where the reverse diffusion water is separated and dried is discharged out of the water recovery drain tank 60 from the fuel discharge pipe 30.

  In the steady operation, as shown in FIG. 14, the hydrogen gas discharged from the fuel discharge conduit 30 passes through the open hydrogen circulation electromagnetic valve 34 to supply the second fuel. It is introduced into the pipe line 33 and supplied again to the fuel gas flow path of the fuel cell stack 20 for reuse. Since the hydrogen start / stop solenoid valve 56a is in a closed state, the hydrogen gas discharged from the suction circulation pump 36 is not discharged into the atmosphere through the start fuel discharge conduit 56, but the first 2 is introduced into the fuel supply line 33. Further, since the outside air introduction electromagnetic valve 28 a is also closed, the atmosphere is not introduced into the second fuel supply conduit 33.

  Here, since the fuel discharge line 30 is connected to the side wall of the upper part of the drain tank container 64, only the hydrogen gas in a dry state in which the reverse diffusion water is separated and becomes light is used as the fuel discharge line 30. The water is not discharged. Further, since the fuel discharge pipe 31 and the fuel discharge pipe 30 are connected to the side wall of the upper part of the drain tank container 64 at a position apart from each other, the fuel discharge pipe 31 and the fuel discharge pipe 30 are introduced into the drain tank container 64 from the fuel discharge pipe 31. The gas / liquid mixture does not flow out of the fuel discharge line 30 as it is. As a result, surplus reverse diffusion water that has permeated into the fuel gas flow path can be trapped appropriately, and surplus hydrogen gas can be recovered in a dry state and reused.

  On the other hand, the reverse diffusion water separated and dropped from the gas-liquid mixture is stored as stored water 65 in the lower part of the drain tank container 64. Since the capacity of the drain tank container 64 is set to be larger than the expected amount of reverse diffusion water, the vehicle on which the fuel cell stack 20 is mounted once fills the fuel storage means 73 with hydrogen gas as fuel. It is not necessary to drain water from the water recovery drain tank 60 after the vehicle travels until the next time hydrogen gas is charged into the fuel storage means 73.

  Next, the operation when stopping the operation of the fuel cell system will be described. In this case, as shown in FIG. 15, the control means first closes the fuel supply electromagnetic valve 26 and the hydrogen circulation electromagnetic valve 34 to shut off the supply of hydrogen gas to the fuel gas flow path. Then, the hydrogen start / stop solenoid valve 56a is opened, and the hydrogen gas in the fuel gas flow path is discharged from the start fuel discharge pipe 56 to the atmosphere. Thereby, the stored water 65 stored in the water recovery drain tank 60 is also discharged.

  In this case, since the suction circulation pump 36 is operating, the hydrogen gas remaining in the fuel cell stack 20, the drain tank container 64, the second fuel supply pipe 33, the fuel discharge pipe 30 and the fuel discharge pipe 31. Is sucked by the suction circulation pump 36 and discharged into the atmosphere from the starting fuel discharge line 56. And since the inside of a fuel gas flow path becomes a negative pressure, hydrogen gas is reliably removed from the fuel gas flow path quickly and discharged. In the case where a hydrogen combustor is disposed in the startup fuel discharge line 56, the hydrogen gas discharged into the atmosphere is burned, combined with oxygen, and discharged as water.

  The pressure of hydrogen gas in the fuel gas flow path is detected by a pressure sensor 78. In this case, since the pressure of the hydrogen gas can be considered to be the same in the range from the fuel supply solenoid valve 26 to the suction circulation pump 36 in the path through which the hydrogen gas flows, the pressure sensor 78 is disposed within the range. Then, the pressure detected by the pressure sensor 78 is equal to the pressure of the fuel gas flow path of the fuel cell stack 20.

  Subsequently, in this state, the pressure of the hydrogen gas in the fuel gas flow path becomes a predetermined pressure, for example, 0.01 [MPa abs] or less, or a predetermined time which is a time until the pressure reaches the predetermined pressure, For example, 40 seconds elapse. In this case, since the predetermined pressure is a considerable negative pressure, hydrogen gas does not substantially remain in the fuel passage in the fuel gas passage.

  The predetermined time is a time until the pressure of the hydrogen gas in the fuel gas channel becomes the predetermined pressure. The predetermined time and the predetermined voltage are obtained in advance by experiments.

  Then, when the pressure of the hydrogen gas in the fuel gas flow path becomes equal to or lower than the predetermined pressure or when the predetermined time has elapsed, as shown in FIG. 16, the control means opens the outside air introduction electromagnetic valve 28a. Then, air is introduced into the fuel gas flow path. In this case, since the fuel supply electromagnetic valve 26 is in a closed state, the introduced air does not flow toward the fuel storage means 73. Thereby, the fuel gas flow path of the fuel cell stack 20 is filled with air. Since the air passes through the air filter 28b and is filtered, it does not contain dust, impurities, harmful gases, etc. that exist in the atmosphere. Therefore, a member such as a catalyst in the fuel gas passage is not contaminated or altered by the dust, impurities, harmful gas, or the like.

  In the present embodiment, since the drain tank container 64 is connected to the fuel cell stack 20, when air is introduced into the fuel cell stack 20, it remains in the fuel gas flow path of the fuel cell stack 20. The hydrogen gas is rapidly driven into the drain tank container 64. Therefore, when air is introduced into the fuel cell stack 20, the hydrogen gas remaining in the fuel gas channel is introduced even if the fuel gas channel of the fuel cell stack 20 is not evacuated. It will not be mixed with oxygen in the air. Therefore, no potential shift occurs in the unit cell 10A, so that the catalyst particles are not eluted and the performance of the fuel cell stack 20 is not deteriorated.

  Subsequently, in this state, the output of the fuel cell stack 20 becomes a predetermined voltage, for example, 5 [V] or less, or a predetermined time, for example, 10 seconds elapses until the output becomes the predetermined voltage. Wait until Here, the predetermined voltage is such that no hydrogen gas remains in the fuel gas flow path, the air is filled, and a potential difference is not substantially generated between the fuel electrode 13 and the air electrode 12. The corresponding output voltage.

  When the output of the fuel cell stack 20 becomes equal to or lower than the predetermined voltage or the predetermined time has elapsed, the control means stops the suction circulation pump 36, closes the outside air introduction electromagnetic valve 28a, and finally oxidizes. The agent supply source 75 is stopped. As a result, the output of the fuel cell stack 20 is stopped.

  As described above, in the present embodiment, the gas-liquid mixture of the reverse diffusion water and hydrogen gas that has become surplus in the fuel gas flow path is sucked by the suction circulation pump 36 and discharged to the outside of the fuel cell stack 20. It has become so. Therefore, it is possible to prevent clogging that is hindered by reverse diffusion water in which the circulation of hydrogen gas in the fuel gas flow path becomes excessive, and to stably supply hydrogen gas as fuel to the surface of the fuel electrode 13. Can do.

  Further, surplus reverse diffusion water is separated from hydrogen gas by the water recovery drain tank 60 and recovered in the water tank 52, so that it can be reused effectively. Thereby, the shortage of the water sprayed in order to humidify the air electrode 12 of the fuel cell stack 20 can be compensated, and the water tank 52 can be reduced in size and weight.

  Furthermore, since the reverse diffusion water mixed with the surplus hydrogen gas is separated by the water recovery drain tank 60, the surplus hydrogen gas can be recovered and reused. Thereby, the fuel consumption of the fuel cell stack 20 can be suppressed.

  Further, the capacity of the drain tank container 64 of the water recovery drain tank 60 is set to be larger than the amount of reverse diffusion water estimated based on the amount of fuel mounted on the vehicle. Therefore, since it is not necessary to detect or control the water level of the stored water 65 stored in the drain tank container 64, the configuration of the water recovery drain tank 60 can be simplified and the cost can be reduced. it can. Moreover, it is not necessary to discharge hydrogen from the water recovery drain tank 60 to the atmosphere during normal operation of the vehicle.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

It is a figure which shows the structure of the fuel cell system in embodiment of this invention. It is a figure which shows the structure of the fuel cell stack in embodiment of this invention. It is a figure which shows the structure of the cell module of the fuel cell in embodiment of this invention. It is a 1st figure which shows the structure of the separator of the fuel cell in embodiment of this invention. It is a 2nd figure which shows the structure of the separator of the fuel cell in embodiment of this invention. It is a 1st expanded sectional view which shows the structure of the cell module of the fuel cell in embodiment of this invention. It is a 2nd expanded sectional view which shows the structure of the cell module of the fuel cell in embodiment of this invention. It is an expansion perspective view which shows the structure of the unit cell of the fuel cell in embodiment of this invention. It is a schematic cross section which shows the structure of the unit cell of the fuel cell in embodiment of this invention. It is a figure which shows the structure of the water collection | recovery drain tank in embodiment of this invention. It is a figure which shows the change of the water recovery amount of the water recovery drain tank in embodiment of this invention. It is a figure which shows the change of the water collection | recovery amount of the water collection | recovery drain tank when the solid polymer electrolyte membrane in embodiment of this invention gets wet. It is a figure which shows the change of the quantity of reverse diffusion water with respect to the amount of hydrogen consumption in embodiment of this invention. It is a 1st figure explaining operation | movement of the fuel cell system in embodiment of this invention. It is a 2nd figure explaining operation | movement of the fuel cell system in embodiment of this invention. It is a 3rd figure explaining operation | movement of the fuel cell system in embodiment of this invention.

Explanation of symbols

10A Unit cell 10B Separator 11 Solid polymer electrolyte membrane 12 Air electrode 13 Fuel electrode 20 Fuel cell stack 21 First fuel supply line 30, 31 Fuel discharge line 33 Second fuel supply line 36 Suction circulation pump 48 Fuel chamber 60 Water recovery drain tank

Claims (5)

(A) a fuel cell stack in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, and is stacked with a separator having a fuel gas flow path formed along the fuel electrode;
(B) a fuel supply line connected to the inlet of the fuel gas flow path;
(C) a fuel discharge line having one end connected to the outlet of the fuel gas flow path and the other end connected to the fuel supply line;
(D) a pump provided in the fuel discharge pipe, for discharging back diffusion water from the fuel electrode to the fuel discharge pipe and supplying the fuel gas discharged from the fuel gas flow path to the fuel supply pipe When,
(E) A recovery container provided in the fuel discharge pipe and having a capacity larger than the amount of reverse diffusion water recovered when all the fuel gas stored in the fuel storage means connected to the fuel supply pipe is consumed And a water discharge pipe that is provided at a lower portion of the recovery container, is shut off from the outside during operation of the fuel cell stack, and is opened to the outside when the operation of the fuel cell stack is stopped. Fuel cell system. (A) having an exhaust pipe having one end connected to the fuel discharge pipe and the other end opened to the atmosphere;
(B) The fuel cell system according to claim 1, wherein the exhaust pipe line includes an exhaust on-off valve that is opened when the operation of the fuel cell stack is stopped. The fuel cell system according to claim 2, wherein the exhaust pipe includes a hydrogen combustor. The fuel cell system according to any one of claims 1 to 3, wherein the fuel cell stack is a power source of a vehicle, and the amount of reverse diffusion water is estimated based on an amount of fuel gas mounted on the vehicle. (A) A method of operating a fuel cell system in which fuel gas is supplied from a fuel storage means to a fuel gas passage of a fuel cell stack mounted on a vehicle, and fuel gas discharged as an unreacted component is returned to the fuel gas passage. Because
(B) connecting the other end of the fuel discharge line, one end of which is connected to the fuel supply line, to the outlet of the fuel gas line, and connecting the fuel supply line to the inlet of the fuel gas line;
(C) to the fuel discharge line, the times container having a capacity greater than despreading water provided to be recovered when consumed all the fuel gas stored before Symbol fuel storage means,
(D) When stopping the operation of the fuel cell stack, by opening the lower portion of the collection container to the outside as well as blocking the conduction of the previous SL fuel discharge line and the fuel supply line, into the collection container the method of operating a fuel cell system, characterized in that the contained despread water discharged into the atmosphere.

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